Access systems generally provide access to restricted means, such as communication systems and data, or to restricted areas such as buildings and departments. There are known in the art access systems which employ integrated circuit (IC) cards, or as more commonly referred to "smart cards", to provide secure access to restricted means or areas.
Smart cards are employed in systems such as pay TV systems and telephone systems. Such systems generally employ one card per unit which is to be accessed, whereby access is enabled whenever a valid smart card is inserted in a card slot.
U.S. Pat. No. 4,709,136 to Watanabe describes an IC card reader/writer apparatus which includes at least two contactors in which IC cards are inserted, respectively, card detecting means for detecting that at least two IC cards have been loaded, and collating means verifying that correct cipher codes of the two IC cards coincide with those inputted externally, respectively, wherein access to the contents stored in the IC cards is allowed only when the collation results in coincidence.
U.S. Pat. No. 4,594,663 to Nagata et al describes a credit transaction processing system which processes data related to a commodity entered into by using a card owned by a customer and a recording card owned by a store.
U.S. Pat. No. 5,010,571 to Katznelson describes a system for controlling and accounting for retrieval of data from a CD-ROM memory containing encrypted data files from which retrieval must be authorized.
Various aspects of electronic book technology, representing an attempt to instantiate various qualities of paper-based books in an electronic device, are known in the art. Related technologies include technologies for storing, retrieving, and updating book-like documents in electronic form. The following references described some aspects of electronic book and related technology:
U.S. Pat. No. 4,159,417 to Rubincam; PA1 U.S. Pat. No. 4,160,242 to Fowler et al; PA1 U.S. Pat. No. 4,290,062 to Marti et al; PA1 U.S. Pat. No. 4,350,070 to Bahu; PA1 U.S. Pat. No. 4,589,659 to Yokoi et al; PA1 U.S. Pat. No. 4,639,225 to Washizuka; PA1 U.S. Pat. No. 4,680,459 to Drexler; PA1 U.S. Pat. No. 4,740,912 to Whitaker; PA1 U.S. Pat. No. 4,855,725 to Fernandez; PA1 U.S. Pat. No. 4,917,292 to Drexler; PA1 U.S. Pat. No. 4,937,821 to Boulton; PA1 U.S. Pat. No. 4,985,697 to Boulton; PA1 U.S. Pat. No. 5,113,178 to Yasuda et al; PA1 U.S. Pat. No. 5,167,508 to McTaggart; PA1 U.S. Pat. No. 5,239,665 to Tsuchiya; PA1 U.S. Pat. No. 5,285,496 to Frank et al; PA1 U.S. Pat. No. 5,339,091 to Yamazaki et al; PA1 U.S. Pat. No. 5,371,493 to Sharpe et al; PA1 U.S. Pat. No. 5,413,486 to Burrows et al; PA1 U.S. Pat. No. 5,438,344 to Oliva; PA1 U.S. Pat. No. 5,466,158 to Smith III; PA1 U.S. Pat. No. 5,469,506 to Berson et al; PA1 U.S. Pat. No. 5,484,292 to McTaggart; PA1 U.S. Pat. No. 5,533,124 to Smith et al; PA1 U.S. Pat. No. 5,534,888 to Lebby et al; PA1 U.S. Pat. No. 5,555,446 to Jasinski; PA1 U.S. Pat. No. 5,625,404 to Grady et al; PA1 U.S. Pat. No. 5,630,103 to Smith et al; PA1 U.S. Pat. No. 5,661,635 to Huffman et al; PA1 U.S. Pat. No. 5,663,748 to Huffman et al; PA1 U.S. Pat. No. 5,689,648 to Diaz et al; PA1 U.S. Pat. No. 5,697,793 to Huffman et al; and PA1 European Patent Application 0 683 613 A2, assigned to AT&T Corp.
The disclosures of all references mentioned above and throughout the present specification are hereby incorporated herein by reference.